1. The Field of the Invention
This invention relates to apparatus used to separate particles consisting of one material from one or more other materials. More particularly, the present invention relates to apparatus and methods utilizing electromagnetic force to separate particles consisting of one electrically conductive material of interest, such as a valuable metal, from other conductive and nonconductive materials.
2. The Prior Art
There are many occasions in scientific and industrial applications where materials must be separated from one another. Particularly in the mining industry, valuable metals must be efficiently separated from other materials which are found in the ore.
In many industrial applications, separation of particles having different sizes and densities relies on the earth's gravity as well as some additional process such as filtration. All such arrangements which have been devised utilizing gravity to separate particles of different densities include one or more drawbacks as are recognized in the art. For example, such arrangements may require water as a carrier for the particles to be separated. Disadvantageously, the water must be removed from the particles after separation. Moreover, in some mining locations, water is not readily available.
In order to provide efficient separation without water, various apparatus and techniques have been proposed which also utilize some electromagnetic properties of materials, rather than density alone, to separate materials. While the task of separating magnetic materials from nonmagnetic materials is a relatively easy one, the task of separating a nonmagnetic materials from other nonmagnetic materials utilizing the magnetic properties of the materials has been the subject of research in the industry. Still, many problems and drawbacks exist with the proposed schemes. Particularly in the mining industry, there have been numerous attempts to separate materials from one another, for example gold from other materials, based on the differing magnetic properties of the materials.
One example of a previous scheme is represented by U.S. Pat. No. 5,057,210 to Julius. The Julius reference recognizes that the creation of eddy currents in conductive materials allows a magnetic field to move a nonmagnetic material. The Julius reference, however, utilizes rotating permanent magnets to generate a changing magnetic field and thus does not recognize critical aspects of the use of induced eddy currents in electrically conductive, nonmagnetic materials as will be explained shortly.
Another example of a previous scheme is represented by U.S. Pat. No. 5,161,695 to Roos. The Roos reference also recognizes that the creation of eddy currents in conductive materials allows a changing magnetic field to move particles of a nonmagnetic material. The Roos reference, however, utilizes permanent magnets, as does the Julius reference, and thus does not recognize critical aspects of utilizing induced eddy currents to cause movement of nonmagnetic particles. The scheme of the Roos reference is ineffective as will be apparent shortly.
Still another example of a prior scheme is found in U.S. Pat. No. 4,238,323 to Zakharova. The Zakharova reference teaches that a ferromagnetic core, and the shape of the core, is critical to the operation of the device. However, ferromagnetic cores such as disclosed in the Zakharova patent cannot operate at increased frequencies at high magnetic field strengths because of resulting huge energy loses causing the core to overheat and lose its magnetic properties. These and other disadvantages of the scheme disclosed in the Zakharova reference will shortly become clear.
Yet another example of a prior scheme is found in U.S. Pat. No. 1,829,565 to Lee. Disadvantageously, the Lee reference does not recognize any relationship between the particle size and the frequency of the applied magnetic field. The Lee patent also does not recognize that electrical resistivity and the size of the particles to be separated is important to separation efficiency.
In view of the shortcomings inherent in the previously proposed schemes to separate nonmagnetic materials using magnetic force, it would be a significant advance in the art to provide a more efficient system and method of separating electrically conductive nonmagnetic materials.